HARTFORD, Conn. (AP) -- Residents of several major Northeast cities are experiencing a fast-moving coastal storm that is bringing a mix of sleet, rain and snow to areas along the busy Interstate 95 corridor this weekend.

The snow that began falling in southeastern Pennsylvania and West Virginia late Friday had become rain and sleet in some areas by early Saturday, and the National Weather Service said Washington, D.C., Delaware and most of Maryland had rain. But conditions in some locations were expected to worsen as the day progressed.

Satellite image taken Thursday shows a storm system over the Atlantic Ocean, now bringing snow and freezing rain to the Northeast. (AP Photo/Weather Underground)

Southern New England could get walloped with the largest amount of snowfall, but temperatures hovering near freezing could make for slippery driving conditions across the region, forecasters warned.

"It's kind of the first one, so it's a good thing it's happening this weekend," weather service meteorologist Bill Simpson in Taunton, Massachusetts, said Friday of the storm. "If this happened during a weekday, it could be really slow and messy."

A winter storm warning was issued Friday for a large portion of central Pennsylvania ahead of the storm. Forecasters said a wide area between Gettysburg and Johnstown, stretching from West Virginia through Maryland to just south of State College and Williamsport, could get 5 to 8 inches of snow by Saturday afternoon.

The Maryland State Highway Administration warned motorists that travel may become hazardous. The agency said it would have salt, snowplows and chain saws at the ready in case of fallen trees.

As the storm moves northeast along the Eastern Seaboard, it is expected to drop 2 to 4 inches of snow and ice in Philadelphia on Saturday before turning over to rain. It is forecast to bring 3 to 4 inches of snow to New York City and 4 to 6 inches to Boston, with higher amounts in central Massachusetts, before moving out to sea by early Sunday.

In New York City, the Metropolitan Transportation Authority said it would be deploying super-powered snow throwers and retired subway cars modified with de-icing equipment to keep bus routes and subway rails clear. MTA workers also were set to spread salt and clear railroad platforms and stairs of snow, the agency said.

"We ask that each and every single Boston resident look after their neighbor, be it someone you see outdoors or someone living next door," he said.

Connecticut has plenty of salt and snow-treatment chemicals stockpiled around the state and a fleet of 632 plow trucks ready to go, Department of Transportation spokesman Kevin Nursick said. He said crews have been pre-treating some highways and bridges, but there already is some salt leftover from recent, smaller storms.

"We don't need to go full tilt," he said.

Meteorologist Peter Wichrowski in Upton, New York, said snow likely would start to fall in New York City in the early morning hours of Saturday, with a mix of rain and maybe a little sleet along the coastal areas. He said snowfall totals were expected to be around 1 to 2 inches across eastern Long Island.

Baltimore and Washington were expected to get only rain as temperatures hover just above freezing. Forecasters expect snow will be heaviest in western Maryland and to the north on Saturday. The Maryland Transit Administration says it is working to keep buses, trains and cars moving this weekend during the winter weather

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Associated Press writers Albert Stumm in Philadelphia and Deepti Hajela in New York contributed to this report.